As mobile devices have been increasingly developed, and the demand for such mobile devices has increased, the demand for secondary batteries has also sharply increased. Among such secondary batteries is a lithium secondary battery exhibiting high energy density and operating voltage and excellent charge retention and service-life characteristics, which has been widely used as an energy source for various electronic products as well as mobile devices.
However, various kinds of combustible materials are contained in the lithium secondary battery. As a result, the lithium secondary battery may be heated or explode due to the overcharge of the battery, the overcurrent in the battery, or external physical impact. That is, the safety of the lithium secondary battery is very low. Consequently, safety elements, such as a positive temperature coefficient (PTC) element and a protection circuit module (PCM), to effectively control an abnormal state of the lithium secondary battery, such as the overcharge of the lithium secondary battery or the overcurrent in the lithium secondary battery, are mounted to a battery cell in a state in which the safety elements are connected to the battery cell.
Generally, a PCM is inserted into a top cap housing and is coupled to the top cap housing by welding or soldering. That is, the PCM is inserted into the top cap housing, in which a connecter is assembled, and is coupled to the top cap housing by welding or soldering so that the PCM is connected to a top cap assembly, and the top cap assembly is coupled to a battery cell. In this way, a battery pack is manufactured.
When a welding or soldering process is carried out, however, more precise work is required due to a compact structure of the secondary battery with the result that a defect rate may be increased. Also, a battery pack assembly process is complicated due to processes related to soldering, such as soldering, washing, and external appearance inspection of solder.
In addition, soldering tolerance is unavoidable, and therefore, it is necessary to increase the length of electric components constituting the battery pack with the result that the capacity of the battery cell is reduced.
Therefore, there is a high necessity for a technology that is capable of stably coupling members mounted to the upper end of a battery cell without soldering and, at the same time, of simplifying an assembly process, thereby minimizing manufacturing cost.